Impact clutch



April 30, 1968 A KAMAN 3,380,539

IMPACT CLUTCH Filed Sept. 8, 1964 5 Sheets-Sheet l J: w.) M I 15 INVENTOR. FRANK A. KAMAN April 30, 1968 F. A. KAMAN 3,380,539

IMPACT CLUTCH Filed Sept. 8, 1964 s Sheets-Sheet 2 INVENTOR. FRANK A. KAMAN April 30, 1968 AN 3,380,539

65 INVENTOR FRANK A. KAMAN 4944601, ,flizmwmfl (9M Mitt a s.

United States Patent 3,380,539 IMPACT CLUTCH Frank A. Kaman, Prospect Heights, 111., assignor to Skil Corporation, Chicago, 11]., a corporation of Delaware Filed Sept. 8, 1964, Ser. No. 394,682 8 Claims. (Cl. 17393.5)

This invention relates in a general way to impact clutches of the type adapted automatically to deliver in rapid succession a series of rotational impact blows to a tool spindle for running a nut or the like, and more particularly the invention relates to a new and improved impact clutch of the type which permits greater acceleration of the clutch driving motor thereby to increase substantially the magnitude of the impact blows.

The impact clutch of this invention is an improvement on the impact clutch disclosed in Amtsberg Patent No. 2,285,638. The clutch in the aforementioned patent includes a spindle having an axially extending anvil provided with a pair of diametrically oppositely disposed jaws each having a pair of oppositely facing striking faces. A cage-like member carries a pair of oppositey disposed hammers for rotation with the anvil and for rotation relative thereto. The hammers are supported by the cage-like member for rocking movement between clutched and declutched positions, and the hammers each include pairs of longitudinally extending jaws adapted in the clutched positions of the hammers to strike the jaws on the anvil for delivering to the anvil a rotary impact blow. The jaws on the anvil and the hammers are adapted and arranged so that the hammers are clutched once every one-half revolution of the cage and hammers relative to the anvil. In other words, for every revolution of the cage and hammers relative to the anvil, two impact blows are delivered to the anvil through the jaws thereof.

In the Amtsberg clutch, a driving cam, directly driven by a motor such as a pneumatic or electric motor, drives both the hammers and their cage-like support member. As the hammers and their support member are allowed to rotate only one-half revolution relative to the anvil during impacting the same, the driving motor has little opportunity to accelerate to any great degree. This is of special significance when a pneumatic motor is used to power such a clutch, since as is known to those skilled in the art, a pneumatic motor must be allowed to accelerate through at least one complete revolution to develop torque anywhere near its maximum torque. Accordingly, when a pneumatic motor is used with the Amtsberg impact clutch just described, the magnitude of the impact blows is considerably less than that which would be possible if the clutch driving motor was allowed to rotate through an arc greater than 180 between impact blows. The instant invention is concerned with a unique improvement of the Amtsberg clutch whereby the driving motor for the clutch is allowed greater acceleration between impact blows thereby to increase substantially the magnitude of the latter.

It is a primary object of the present invention to provide a new and improved impact clutch of the type described which is adapted to deliver to the spindle an impact blow once every revolution of the hammers relative to the anvil, thereby to permit the driving motor to accelerate through one revolution after each impact blow.

Another object of the present invention is the provision of a new and improved impact clutch of the type described which is adapted to deliver to the spindle is balanced impact blow once every revolution of the hammers in either direction relative to the anvil, thereby to permit the driving motor to accelerate through one revolution after every impact blow.

Still another object of the present invention is the provision of new and improved jaw construction for the tion disclosing a preferred embodiment of the invention which is illustrated in the accompanying drawings.

In the drawings: FIG. 1 is a longitudinal section of a tool (fragmentarily illustrated) incorporating an embodiment of the impact clutch of this invention;

FIG. 2 is an exploded clutch;

FIG. 3 is a side elevational view of the spindle which ncludes an axially extending anvil provided with pairs of impact receiving jaws;

FIG. 4 is an enlarged section taken along line 4-4 of FIG. 3;

FIG. 5 is an enlarged section taken along line 5-5 of FIG. 3;

FIG. 6 is a side elevational view of one of the hammers of the impact clutch;

FIG. 7 is a section taken along line 7-7 of FIG. 6;

FIG. 8 is a side elevational view of the other hammer of the impact clutch;

FIG. 9 is a section taken along line 9-9 of FIG. 8;

FIGS. 10a and 10b are sections taken perpendicular to the axis of rotation of the spindle, with only the anvil and the hammers being shown, respectively illustrating both hammers at the moment of impact with the anvil aws;

FIG. 10c is a section corresponding to FIGS. 10a and 10b and taken perpendicular to the axis of rotation of the spindle, with only the driving cam and cooperating projections on both hammers being shown, illustrating the relationship between the driving cam and hammer projections at the moment of impact of the hammers with the anvil jaws;

FIGS. 11a, 11b and are similar to respective FIGS. 10a, 10b and 100, illustrating the relationship of the various parts just slightly after the moment of impact;

FIGS. 12a, 12b and are similar to respective FIGS. 10a, 10b and 100, illustrating the relationship of the various parts after the hammers have rotated approximately three-quarters of a revolution from their impact position; and

FIGS. 13a, 13b and are similar to respective FIGS. 10a, 10b and ICC, illustrating the relationship of the various parts just slightly prior to the moment of impact.

Referring now to the drawings and particularly to FIG. 1, a power tool, namely an impact wrench, incorporating the impact clutch of this invention will be seen to include a casing or housing having an impact clutch enclosing portion 10 and a handle/motor enclosing portion 12 (fragmentarily shown). Casing portion 12 encloses a suitable motor (not shown), such as a pneumatic motor, which drives a gear 14 ro tatably supported in a ball bearing assembly 15. It will be understood. that its pneumatic motor is of the type adapted to be driven in either rotary direction by a suitable source of air, and it will be further understood that housing portion 12 includes suitable means for connecting such a motor with a source of air as well as trigger or operating lever means for controlling the speed and direction of rotation of the motor. Gear 14 includes bevel teeth in meshing engagement with complementary shaped teeth of a driven gear 16. As noted in FIG. 2, gear 16 includes a central, hexagonal shaped opening 17. Opening 17 nonrota'tably engages a complementary shaped portion 18 of a driving cam 26.

Looking now to FIG. 2, which shows the elements of the impact clutch of this invention, the latter includes the perspective View of the impact just mentioned driving cam 20, a cage member 22, hammers 24, 25 and their respective supporting pins 27, 2S, and finally a spindle 36 including an integral, axially extending anvil 32.

Referring now both to FIGS. 1 and 2, spindle 36 includes a cylindrical portion 33 rotatably supported in a bearing sleeve 34, which sleeve is fixed in an opening 35 in the nose of tool housing portions 10. Cylindrical portion 33 includes a socket 36 which is preferably hexagonal in cross section. Spindle 30 further includes an annular fiange portion 37, one side face of which bears on the inner end of sleeve 34.

As noted in FIG. 1, the free end of anvil 32 of the spindle is rotatably supported in a ball bearing assembly 38 supported in a cylindrical cavity 39 formed in the inner end of tool housing portion 10. Thus, spindle 30 is rotatably mounted in tool housing portion for rotation about the longitudinal central axis of the spindle.

Looking again primarily to FIG. 2, cage 22 includes generally annular, upper and lower portions 40 and 41, respectively, which portions are held in spaced relation by integral legs 42, 43. It will be apparent to those skilled in the art that the cage member could be of other designs or made from a number of separate parts. The cage includes aligned, centrally located openings 45, 46 which adapt the cage to receive anvil 32, opening 46 being rotatably supported on an annular bearing 48 formed integral with spindle 30. Driven cam 20 includes a cylindrical portion 56 (this portion is cylindrical with the exception of a pair of diametrically oppositely disposed fiat portions 51) which rotatably engages cylindrical opening 45 in cage 22. Driven cam 20 includes a central through opening 52 in which a portion of the anvil adjacent the free end thereof is rotatably received. It will be apparent then that driving cam 20 acts, among other things, as a bearing insert for rotatably mounting end portion 40 of cage 22 on anvil 32.

As mentioned above, opening 17 in gear 16 engages complementary shaped portion 18 of the driving cam, thereby securing the driving cam 20 and gear 16 together for driving of the former by the latter. The smaller annular face of gear 16 engages an annular face 54 formed around opening 45 of cage 22. The larger annular face of gear 16 is engaged by a spaced bearing 55 (FIG. I), which bearing permits rotation of gear 16 and maintains the latter in predetermined relation from ball bearing assembly 38 and the inner end of housing portion 10.

Hammer 24 includes a longitudinally extending opening 57 rotatably receiving pin 27, which pin has respective opposite ends thereof adapted to be received in openings 58 and 59 formed in respective portions 40 and 41 of the cage. Opening 58 is of reduced size at its opening into the outer surface of portion 40, thereby to prevent movement of pin 27 through this opening. The other end of pin 27 is prevented from moving axially of the cage, when the impact clutch is assembled, by its engagement with annular flange 37 of the spindle. As noted in FIG. 1, pin 27 mounts hammer 24 to the cage and supports the former for limited rocking movement about an axis defined by the longitudinal central axis of the pin.

Hammer 24 includes a generally rectangular shaped projection 61 extending from one end thereof, which projection is received in a notch 62 formed in a flange of driving cam 20. The dimensions of projection 61 relative to the dimensions of notch 62 are such that hammer 24 is permitted limited rocking movement about its supporting pin when projection 61 is received Within the notch but the engagement between the projection and notch 62 of the driving cam is such that the latter upon being rotated or driven is adapted under certain conditions, to be explained hereinbelow, to rock the hammer about the axis defined by pin 27.

Hammer 25 is identical with hammer 24, with the exception of the configuration of the jaws thereof to be explained hereinbelow, and includes a longitudinal central opening 64 rotatably engageable with pin 28, which pin is held in cage 22in the same manner as pin 27 and in diametrically oppositely disposed relation from the latter. Hammer 25 includes a projection 65 received within 'a notch 66 of driving cam 20, which notch is diametrically oppositely disposed from notch 62 of the driving cam. It should now be apparent that hammers 24, 25 are carried by the cage for rotation about the spindle and for rocking movement about separate parallel axes defined by the longitudinal central axes of pins 27, 28.

The unique arrangement of the jaws on the anvil and the hammers will now be described.

Referring to FIGS. 2, 8 and 9, hammer 24 will be seen to be generally arcuate in transverse cross section. Hammer 24 includes a longitudinally extending fiat surface 24a, defining the back of the hammer, and wing portions 24b, 24c. The hammer includes an annular boss 24d at the lower end of the hammer, which boss is concentric with bore 57 and acts as a bearing surface for supporting the hammer on the portion 41 of the cage. This boss rests on the upper surface of annular portion 41 of cage 22 when the hammer is mounted in place. Hammer 24 includes a pair of jaws 70, 71 at the approximate longitudinal midpoint of the hammer, which jaws are separated and partly defined by a semicylindrical cam surface 72. The central axis of semicylindrical cam surface 72 is eccentric with respect to the central axis of the anvil (when the hammer is mounted in place in a neutral position on the cage, i.e. when the hammer is symmetrical with respect to a radius extending from the center of the anvil and passing through the center of pin 27); the central axis of cam surface 72 is spaced outwardly from the central axis of the anvil. Or stated another way, the radius of cam surface 72 is less than the radius of the anvil taken through one of the jaws thereof. Jaws 70 and 71 include and are partly defined by cam surfaces 70a and 71a.

Now looking to FIGS. 2, 6 and 7, hammer 25 will be seen to include a first pair of jaws 75, 76, and a second pair of jaws 77, 78. Jaws 75, 76 and 77, 78 are identical in cross section with each other, as well as being identical in cross section with jaws 70, 71 of hammer 24. Jaws 75, 76 are separated and partly defined by a semi-cylindrical cam surface 81. In like manner, jaws 77, 78 are partly defined and separated by a semi-cylindrical cam surface 81. Jaws 75, 76 include cam surfaces 75a, 76a. Similarly, jaws 77, 78 include cam surfaces 77a, 78a. Other than the arrangement of the jaws so far described, hammers 24 and 25 are identical. Thus hammer 25 includes a fiat back 25a, wing portions 25b, 25c and a bearing boss 25d. At this time it should be mentioned that both hammers are symmetrical in transverse cross section about center lines intersecting the centers of bores 57, 64 at right angles with flat surfaces 24a, 25a.

As noted in FIG. 6, the length of jaws 75, 76 longitudinally of the hammer is somewhat less than the corresponding length of jaws 77, 78. Now looking to FIGS. 6 and 8, it will be noted that the length of jaws 70, 71 is somewhat greater than the length of jaws 77, 78 of hammer 25. Preferably, the combined length of jaws 75, 76 and 77, 78 is substantially the same as the length of jaws 70, 71 of hammer 24, thereby to provide hammers of substantially the same mass. This relationship between the mass of the hammers provides balanced impact blows to the anvil.

Now looking to FIGS. 2 and 3-5, the anvil will be seen to include three pairs of jaws arranged in series axially of the anvil. The anvil includes a first pair of jaws and 86, which jaws are formed integrally of the anvil and include respective striking faces 85a, 86a, facing in opposite directions of rotation of the anvil. The anvil includes a second or intermediate pair of jaws 88 'and 89 (FIG. 4), which jaws include respective striking faces 88a, 89a, facing in opposite directions of rotation of the anvil. From reference to FIGS. 4 and 5, it should be apparent that the cross section of the anvil through jaws 85, 86 is the same as the cross section of the anvil through jaws 88, 89, except that the latter section is rotated 180 from the section through jaws 85, 86.

The anvil includes a third pair of jaws 91, 92, which jaws have striking faces 91a, 92a facing in opposite directions of rotation of the anvil. Jaws 91, 92 are identical in cross section with jaws 85, 86 of the anvil and are in axial alignment with the latter.

As best noted in FIG. 3, the lengths of the various pairs of jaws are different. Anvil jaws 85, 86 are of a length substantially the same as hammer jaws 75, 76 for cooperating with the same as will be explained below, In like manner, anvil jaws 91, 92 have a length substantially the same as hammer jaws 77, 78 for cooperating with the latter. Anvil jaws 88, 89 have a length which is generally the same as the length of the hammer jaws 70, 71. It is important to note, however, that the length of anvil jaws 88, 89 is less than the distance between hammer jaws 75, 76 and 77, 78 as measured longitudinally of hammer 25. This permits the jaws on hammer 25 to clear anvil jaws 88, 89.

At this point it should be mentioned that hammer jaw 70 is adapted to cooperate with anvil jaw 88, and hammer jaw 71 is adapted to cooperate with anvil jaw 89. Hammer jaws 75 and 77 are adapted to cooperate with anvil jaws 85 and 91, respectively, when the hammer rotates in one direction relative to the anvil, and hammer jaws 76 and 78 are adapted to cooperate with anvil jaws 86 and 92, respectively, when the hammer rotates in an opposite direction relative to the anvil.

The operation of the impact clutch of this invention will now be described. For an understanding of the operation of the impact clutch, particular reference should be made to FIGS. -13. In these figures, which are largely diagrammatic, hammer jaws 77, 78 and anvil jaws 91, 92 are not shown. It will be understood, however, that the operation of these jaws is exactly the same as hammer jaws 75, 76 and cooperating anvil jaws 85 and 86.

Assume that the hammers are in the positions illustrated in FIGS. 10a and 10b, i.e., hammer face 75a is in engagement with anvil face 85a, and hammer face 70a is in engagement with anvil face 88a. Assume further that driving cam is rotated in a clockwise direction (looking at FIGS. 10-13). Notches 62 and 66 of the driving cam engage respective projections 61, 65 of the hammers and rotate the latter about the central axis of the anvil. The cage of course is carried along in rotation with the hammers. Because of the engagement between the hammers and the anvil as illustrated in FIGS. 10a and 10b, the anvil is rotated along with the hammers. In other words, during this stage of operation spindle 30 is directly rotated by the hammers.

Assume further, that socket 36 of spindle 30 has engaged therein a fastener, such as a nut (not shown) to be run. If the resistance to rotation of the nut is relatively slight, the parts of the clutch will remain for a considerable period of time in their positions illustrated in FIGS. 10a, 10b and 100. The hammers remain in these positions mainly due to the friction between the contacting faces of the various jaws. The hammers also tend to remain in this position due to the effect of centrifugal force on the hammers. As noted in FIG. 100, as hammer is rotated in a clockwise direction about the central axis of the anvil, the center of gravity of hammer 25, which is indicated by numeral 95, is located relative to the pivot axis of the hammer so that the hammer tends to rock in a clockwise direction about pin 28, thereby to force jaw 75 into engagement with anvil jaw 85. Hammer 24 is effected by centrifugal force in the same manner.

The planes of contact between the hammer and anvil jaws are such that initial rocking movement of the hammers away from their FIGS. 10a and 10b positions must be accompanied by a slight counterclockwise movement of the cage and pivot pins supporting the hammers. Op-

position by the clockwise driving force to such counterclockwise movement supplements the effect of the frictional forces between the jaws for holding them in their FIGS. 10a and 10b positions.

As the resistance to rotation of the nut being driven increases to a certain point, the resistance to further rotation of the spindle increases accordingly. This resistance to rotation is transferred to the hammers by reason of the contact of the jaws of the latter with the anvil jaws. This resistance to rotation of the hammers increases the pressure between the notches of the driving cam and respective projections on the hammer dogs. As noted in FIG. 10c, continued rotation of driving cam 20 with rotation of the hammers being resisted as just described, results in rocking each hammer in a counterclockwise direction about its own pivot axis. When these rocking or de-clutching forces between the notches of the driving cam and the projections of the hammers exceed the combined effect of the frictional forces between the hammer and anvil jaws and the centrifugal force effect described above, the hammers are de-clutched so that the hammer and anvil jaws are no longer in contact. FIGS. 11a, 11b and 11c illustrate the positions of the various parts just after the hammers have been de-clutched and the hammers have continued again a short distance in their clockwise direction about the axis of the anvil.

The driving cam continues to rotate the hammers about the anvil as rotation of the latter is being prevented by the resistance of rotation of the nut which is received in spindle socket 36. As the hammers moved beyond their FIGS. 11a and 11b positions and to their FIGS. 12a and 12b positions (the hammers rotate approximately 240 about the anvil between these two positions), the hammers assume some position between their fully clutched and fully de-clutched positions.

Just after the hammers pass beyond their positions indicated in FIGS. 12a and 1215, they begin to be cammed or rocked into their positions for delivering another impact blow to the anvil. Referring now to FIGS. 12a and 13a, the camming or rocking hammer 25 is accomplished as follows.

As hammer 25 begins to rotate around anvil jaw 86, the trailing portion of semi-cylindrical portion of the hammer contacts and begins to ride along the back of anvil jaw 86. It will be recalled that the central axis of semi-cylindrical cam surface '80 is eccentric with respect to the central axis of the anvil. Because of this eccentricity, the engagement between the back of the jaw and the semicylindrical cam surface of the hammer tends to cam or rock the hammer in a clockwise direction about its pivot pin 28 as the hammer moves in a clockwise direction about the central axis of the anvil. As noted in FIG. 13a, as the trailing portion of semi-cylindrical cam surface 80 of hammer 25 rides over the outermost portion of anvil jaw 86, the hammer is cammed or rocked such that striking face 75a thereof is in a position for striking face a of anvil jaw 85 upon continued rotation of the hammer about the anvil. As hammer 25 continues in its rotation about the anvil, face 75a of hammer jaw 75 strikes face 85a of anvil jaw 85 for delivering a rotary impact blow to the anvil. Of course, at the same time jaw face 77a of hammer 25 strikes anvil jaw face 91a.

Referring now to FIGS. 12b and 13b, it will be understood that hammer 24 is rocked or cammed into position for delivering an impact blow to the anvil in the same manner just described in connection with hammer 25. FIG. 10b shows the position of hammer 24 as jaw face 70a thereof strikes anvil jaw face 88a. It will be understood that jaw face 70a of hammer 24 strikes anvil jaw face 88a at substantially the same time as jaw faces 75:: and 77a of hammer 25 strike respective anv-il jaw faces 85a and 91a. In other words, the hammers deliver impact blows to the anvil at substantially the same time. It will be realized that it is impossible to manufacture and machine the various clutch parts so that the impact blows delivered by the hammers occur at precisely the same time. However, for all practical purposes it may be considered that the impact blows from both hammers are delivered to the anvil at the same time.

As noted in FIGS. 13c and 100, as the hammers are rocked into their positions for delivering the next impact blow to the anvil, projections 61, 65 of the hammers are cocked within respective notches 62, 66 of driving cam 20. As the jaws of the hammers strike the anvil jaws in delivering an impact blow to the anvil, the resistance to rota-tion of the hammers about the anvil is of course resisted as rotation of the anvil is in turn resisted by reason of the engagement with spindle socket 36 with a fastener being run. As the driving power is continued to be transmitted to driving cam through gear 16, 14, etc., the trailing side walls of the driving cam notches engage the adjacent side walls of the projections of the hammers for rocking the hammers in a counterclockwise direction about their respective axes of pivot as defined by pins 27, 28. This action results in freeing or separating the leading hammer jaws from the anvil jaws thereby allowing the hammers to continue in their rotation about the anvil after their momentary interruption of rotation caused in delivering an impact blow to the anvil through the jaws thereof. As will be recalled from above, there is a slight retrograde movement of the pivot axes upon separation of the jaws thereof from the anvil jaws. After the hammer jaws have been separated from the anvil jaws as just described, the hammers then continue in their rotation about the anvil for delivering another impact blow to the latter in the manner described above.

As mentioned above, the combined longitudinal length of the jaws of hammer is substantially the same as the corresponding length of the jaws of hammer 24 to provide hammers of substantially the same mass. Therefore, the magnitude of the impact blow delivered by the dual jaws of hammer 25 is substantially the same as the magnitude of the impact blow delivered by the single jaw of hammer 24. This of course results in a balanced impact blow being subjected to the anvil.

It will also be recalled that the longitudinal length of jaws 77, 78 of hammer 25 is slightly greater than the corresponding length of jaws 75, 76. This shifts the center of gravity of hammer 2S nearer jaws '77, 78 thereof to increase the magnitude of the impacts delivered by these jaws. Accordingly, the impact blows received by anvil jaws 91, 92 are increased; this is desirable since these anvil jaws are nearest the portion of the spindle (socket 36) which delivers torque to a fastener being run.

It should be apparent that the operation of the impact clutch of this invention is the same when the hammers are rotated in a counterclockwise direction about anvil 32. When the hammers are rotated in a counterclockwise direction about the anvil, the impact blow is delivered to the latter by engagement of jaw face 71a of hammer 24 with anvil jaw face 92a, and jaw faces 76a and 78a of hammer 25 with anvil jaw faces 86a and 92a, respectively.

By reason of the unique arrangement of the jaws on the anvil and the hammers in the impact clutch of this invention, during operation of the latter the impact blows are delivered to the anvil only once for every revolution of the hammers relative to the anvil in either direction. Accordingly, the motor driving the hammers in their path of rotation about the anvil is allowed to accelerate through one complete revolution before rotation of the motor is abruptly halted by reason of engagement of the hammer jaws with the anvil jaws. As the driving motor is allowed to accelerate through one complete revolution, the torque developed by the latter at the moment of collision of the jaws is much greater than would be possible it the motor only rotated through one-half revolution. The impact clutch of this invention is therefore capable of delivering extremely powerful rotary impacts to the spindle for running a fastener or the like. Or viewed another way, the driving motor may be made smaller than would be possible when using prior art impact clutches which deliver impact blows once every one-half revolution. The impact clutch of this invention in being capable of being powered by a smaller motor, readily lends itself to the design and production of lightweight and compact wrenches of which there is a present need in the art because of the complexity of modern-day equipment, such as automobiles for example, in which fasteners are often located in rather confined locations.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not to be so limited. On the contrary, the invention is susceptible of various forms and modifications without departing from the spirit and scope of the appended claims.

I claim:

1. An impact clutch comprising a rotatable anvil having a pair of longitudinally extending jaws both facing in the same rotary direction of the anvil and being offset from each other axially of the anvil, a pair of hammers mounted by common support means for relative rotation around said anvil and for rocking movement, between clutched and declut-ched positions, about separate axes parallel with and spaced from the axis of rotation of the anvil, said hammers being of substantially the same length and being in alignment with each other axially of the anvil, said hammers each :having a jaw adapted to deliver in the clutched position of .the hammers a rotary impact to said anvil through said jaws thereof, respectively, the jaws on respective hammers being positioned axially thereof such that there is only one pair of jaws in any plane perpendicular to the longitudinal axis of the anvil which impact with each other during relative rotation between the anvil and the hammer in one direction, cam means for simultaneously clutching the hammers once for every revolution of the hammers relative to the anvil thereby to deliver a balanced impact blow to the latter, and separate cam means for tie-clutching the hammers.

2. An impact clutch comprising a rotatable anvil having three pairs of longitudinally extending jaws, which pairs of jaws are arranged in series axially of the anvil, a pair of generally diametrically opposed hammers mounted by common support means for relative rotation around said anvil and for rocking movement, between clutched and de-clut-ched positions, about separate axes parallel with and spaced from the axis of rotation of the anvil, one of said ham mers having one pair of jaws at the approximate longitudinal mid-portion thereof adapted in the clutched position of the hammer to cooperate with with one of the pairs of anvil jaws for delivering a rotary impact blow to the anvil once every revolution of the hammer in either direction relative to the anvil, the other of said hammers having two pairs of jaws adjacent respective opposite ends thereof adapted in the clutched position of the hammer to cooperate with the other two pairs of anvil jaws, respectively, for delivering rotary impact blows .to the anvil once every revolution of the other hammer in either direction relative to the anvil, the hammers being adapted and arranged for delivering the impact blows substantially simultaneously, and means for clutching and de-clutching the hammers.

3. The impact clutch according to claim 2 wherein said hammers have substantially the same mass so that the impact blow delivered by one of said hammers is generally the same in magnitude as .the impact blow delivered by the other of said hammers.

4. An impact clutch comprising a rotatable anvil having a first pair of longitudinally extending jaws, and a second pair of longitudinally extending jaws offset axially of the anvil from the first mentioned pair of jaws, the jaws of each pair of jaws facing in opposite rotary directions of the anvil, a pair of longitudinally extending hammers mounted by common support means for relative rotation around said anvil and for rocking movement, between clutched and de-clutched positions, about separate axes parallel with and spaced from the axis of rotation of the anvil, said hammers being of substantially the same length and being in alignment with each other axially of the anvil, said hammers each having a pair of jaws adapted in the clutched position of the jaws to cooperate with said pairs of anvil jaws, respectively, for delivering balanced rotary impact blows to the anvil, the pairs of jaws on respective hammers being positioned axially thereof such that there is only one pair of jaws in any plane perpendicular to the longitudinal axis of the anvil which impact with each other during relative rotation between the anvil and the hammer in one direction, whereby such impact blows are delivered to the anvil once every revolution of the hammers in either direction relative to the anvil, and cam means for simultaneously clutching and de-clutching the hammers.

5. The impact clutch according to claim 4 wherein said means for clutching and declutching the hammers comprises, cooperating cam surfaces on the anvil and the hammers for clutching the latter upon relative rotation between the hammers and anvil and separate cam means for de-clutching the hammers, which separate cam means include a .drive cam rotatable about the axis of rotation of the anvil and having diametrically oppositely arranged notched portions engageable with respective projections on the hammers for driving and de-clutching the latter.

6. In an impact clutch of the type having a rotatable anvil and means supporting a pair of hammers longitudinally of the anvil for rotation relative to the anvil and for rocking movement between clutched and de-clutched positions about axes parallel with the axis of rotation of the anvil, which hammers are of substantially the same length and are in alignment with each other axially of the anvil, and cam means for clutching and de-clutching the hammers, the improvement which comprises, cooperating jaws on the hammers and the anvil for delivering, substantially simultaneously, impact blows to the latter from both hammers upon simultaneous clutching of the same, the jaws on the anvil and the hammers being longitudinally staggered relative to each other there being only one pair of jaws in any plane perpendicular to the longitudinal axis of the anvil which impact with each other during relative rotation between the anvil and the hammer in one direction so that said hammers each deliver only one impact blow for every revolution of the hammers in either direction relative to the anvil.

7. In an impact clutch of the type having a rotatable anvil and means supporting a pair of generally opposed hammers longitudinally of the anvil for rotation relative to the anvil and for rocking movement between clutched and de-clutched positions about axes parallel with the axis of rotation of the anvil, and cam means for clutching and de-clutching the hammers, the improvement which comprises, said anvil having three pairs of longitudinally extending jaws, which pairs of jaws are arranged in series axially of the anvil, one of said hammers having one pair of jaws at the approximate longitudinal mid-portion thereof adapted in the clutched position of said one hammer to cooperate with one of the pairs of the anvil jaws for delivering a rotary impact blow to the anvil once every revolution of the hammer in either direction relative to the anvil, the other of said hammers having two pairs of jaws adjacent respective opposite ends thereof adapted in the clutched position of said other hammer to cooperate with the other two pairs of anvil jaws, respectively, for delivering rotary impact blows to the anvil once every revolution of the other hammer in either direction relative to the anvil.

8. In an impact clutch of the type having a rotatable anvil and means supporting a pair of hammers longitudinally of the anvil for rotation relative to the anvil and for rocking movement between clutched and declutched positions about axes parallel with the axis of rotation of the anvil, which hammers are of substantially the same length and are in alignment with each other axially of the anvil, and cam means for simultaneously clutching and de-clutching the hammers, the improvement which comprises, said anvil having a first pair of longitudinally extending jaws, and a second pair of longitudinally extending jaws, olfset axially of the anvil from the first mentioned pair of jaws, the jaws of each pair of jaws facing in opposite rotary directions of the anvil, said hammers each having a pair of jaws adapted in the clutched position of the hammers to cooperate with said pairs of anvil jaws, respectively, for delivering balanced rotary impact blows from both hammers to the anvil there being only one pair of jaws in any plane perpendicular to the longitudinal axis of the anvil which impact with each other during relative rotation between the anvil and the hammer in one direction, whereby such impact blows are delivered to the anvil once every revolution of the hammers in either direction relative to the anvil.

References Cited UNITED STATES PATENTS 2,663,395 12/1953 Schmid 81523 2,768,546 10/1956 Amtsberg 17393.5 2,886,997 5/1959 Madsen 173-935 3,144,108 8/1964 Reynolds 17393.5

ERNEST R. PURSER, Primary Examiner. FRED C. MATTERN, Examiner.

L. P. KESSLER, Assistant Examiner. 

1. AN IMPACT CLUTCH COMPRISING A ROTATABLE ANVIL HAVING A PAIR OF LONGITUDINALLY EXTENDING JAWS BOTH FACING IN THE SAME ROTARY DIRECTION OF THE ANVIL AND BEING OFFSET FROM EACH OTHER AXIALLY OF THE ANVIL A PAIR OF HAMMERS MOUNTED BY COMMON SUPPORT MEANS FOR RELATIVE ROTATION AROUND SAID ANVIL AND FOR ROCKING MOVEMENT, BETWEEN CLUTCHED AND DE-CLUTCHED POSITIONS, ABOUT SEPARATE AXES PARALLEL WITH AND SPACED FROM THE AXIS OF ROTATION OF THE ANVIL, SAID HAMMERS BEING OF SUBSTANTIALLY THE SAME LENGTH AND BEING IN ALIGNMENT WITH EACH OTHER AXIALLY OF THE ANVIL, SAID HAMMERS EACH HAVING A JAW ADAPTED TO DELIVER IN THE CLUTCHED POSITION OF THE HAMMERS A ROTARY IMPACT TO SAID ANVIL THROUGH SAID JAWS THEREOF, RESPECTIVELY, THE JAWS ON RESPECTIVE HAMMERS BEING POSITIONED AXIALLY THEREOF SUCH THAT THERE IS ONLY ONE PAIR OF JAWS IN ANY 